1. Field of the Disclosure
The present disclosure generally relates to transmissions including an automated shift-type manual transmission wherein a manual transmission may be automatically operated. In particular, the present disclosure relates to devices to reduce drag torque caused by a viscosity of lubricating oil remaining between clutch discs even when a wet rotary clutch disengages.
2. Description of the Related Art
To form an automated shift-type manual transmission by automating a manual transmission, there must be an automated control for disengaging and engaging a clutch installed to connect and disconnect the engine and transmission. In this regard, a wet rotary clutch is generally used due to its superior controllability.
Japanese Laid-Open Patent Publication No. 2007-092814 discloses an automated shift-type manual transmission comprising a wet rotary clutch. In such transmissions, it is possible to change gear ratios or transition from a neutral mode to a forward or reverse driving mode. A synchromesh mechanism conducts a meshing operation during transition from a neutral mode to a shift mode to provide a desired gear ratio when the wet rotary clutch disengages.
The synchromesh mechanism operates when the wet rotary clutch is disengaged. Because a rotary member at an input of the synchromesh mechanism is rotated by an engine when the wet rotary clutch is engaged, the synchromesh mechanism may not synchronously rotate the rotary member at the input with respect to a rotary member at an output of the synchromesh mechanism which is rotating with a wheel. Thus, the meshing operation wherein the synchromesh mechanism is operated from the neutral mode to the shift mode to provide a desired gear ratio may not be executed due to the relative rotation of the rotary members at the input and output.
However, if the wet rotary clutch disengages, because the rotary member at the input of the synchromesh mechanism is separated from the engine, the synchromesh mechanism may not synchronously rotate the rotary member at the input with respect to the rotary member at the output of the synchromesh mechanism rotating with the wheel. Thus, the meshing operation wherein the synchromesh mechanism is operated from the neutral mode to the shift mode to provide a desired gear ratio may not be executed because there is no relative rotation of the rotary members at the input and output.
The wet rotary clutch is typically supplied with the lubricating oil for cooling or preventing abrasion. The lubricating oil prevents overheating caused by frictional heat generated by a slip in an engagement transition period or prevents abrasion of the clutch disc in the engagement transition period.
However, when the lubricating oil is supplied to the wet rotary clutch, a drag torque occurs due to the viscosity of the lubricating oil between the clutch discs. This happens even when the wet rotary clutch is disengaged.
When the drag torque occurs, the drag torque hinders the torque transferred from the engine to the rotary member at the input of the synchromesh mechanism. Thus, it becomes difficult for the synchromesh mechanism to synchronously rotate the rotary member at the input with respect to the rotary member at the output of the synchromesh mechanism. As such, it becomes difficult to operate the synchromesh mechanism from the neutral mode to the shift mode to provide a desired gear ratio to execute the meshing operation, and thereby it becomes difficult to execute the shifting operation.
To address and resolve the above-mentioned problems, the present disclosure seeks to reduce the drag torque of the wet rotary clutch by thoroughly and rapidly removing the lubricating oil interposed between the clutch discs.